This project is directed toward furthering the understanding of the basic scattering mechanisms of ultrasound in biological tissues including blood and the genesis of textural patterns in B-mode ultrasonograms. Moreover, ultrasonic properties of various contrast media which have been used clinically to enhance the echogenicity of cardiac structures or blood will be measured. Major emphasis will be on in vivo validation of data collected. The information obtained is crucial to the better interpretation of ultrasonic images obtained by commercial scanners and to the realization of quantitative characterization of the state of biological tissues by ultrasound. A quantitative assessment of ultrasonic properties of contrast agents is needed for standardizing the preparation procedure and for the utilization of these agents in quantitative approaches in contrast echocardiography. Work on ultrasonic backscatter from whole blood will continue using a narrow band substitution approach. Ultrasonic properties of various contrast media will be determined in vitro and backscatter of heart perfused with contrast agents will also be measured on dogs in vivo. Backscatter from other tissues will be measured with both a broad band and a narrow band approach. In vitro results obtained previously will be verified on dogs in vivo. Correlation of backscatter to tissue histology will also continue. A prototype static B-scanner will be built to obtain images with propagation effects corrected so that the physical significance of textural patterns can be better understood.